The present invention relates to a field measuring instrument such as a differential pressure/pressure transmitter, an electromagnetic flow meter, a temperature transmitter, or the like which is managed by a communication unit provided at a central location and is used for industrial measurement or the like. More particularly, the invention intends to provide a field measuring instrument which has a microcomputer and is suitable for self-diagnosing operating states of apparatuses in the field measuring instrument and states of measurement data items and the like, for storing the results of the self-diagnosis without a backup power source, and for managing the results of the self-diagnosis and to provide its abnormality managing method.
Hitherto, field measuring instruments having a microcomputer have been well known.
In general, in such apparatuses, a communication device is connected to a line to supply an output current serving as an operating current of, for instance, 4 to 20 mA to the relevant field measuring instrument and digital communication is executed between the field measuring instrument and the communication device, so that a measuring range of the field apparatus and a damping time constant can be set, the inputs and outputs can be monitored, and the self-diagnosis of the field measuring instrument and the like can be executed.
In the field measuring instrument having such a self-diagnosis function, the self-diagnosis of input abnormality, internal circuit abnormality, software abnormality, and the like is always executed. Such abnormality can be discriminated by inquiring the results of the diagnosis from the side of the communication device. However, the result merely indicates the present abnormal state and there is a problem such that it is impossible to know whether an abnormality has occurred in the past or not.